Fueling the Future Economy
One of the largest academic palladium membrane groups in the world: clockwise from front, Federico Guazzone, Research Assistant Professor Ivan Mardilovich, Research Assistant Professor Erik Engwall, Engin Ayturk, Alpna Saini, Professor Ed Ma, Rajkumar Bhandari
A vision of tomorrow’s hydrogen economy could boil down to this: a vehicle, powered by an environmentally friendly fuel cell, pulls up to the pumps at the local “gas” station to refill its tank with pure, inexpensive hydrogen.
For more than a decade, Yi (Ed) Hua Ma has been working to overcome one of the most important obstacles standing in the way of the widespread use of fuel cells: the high cost of producing hydrogen pure enough to power the cells without poisoning their catalysts. The U.S. Department of Energy has set a target price for hydrogen of $1.50 per kilogram to make small-scale applications, such as fuel cell-powered cars, economical; it costs about $5 to produce that much pure hydrogen right now.
Ma, the director of WPI’s Center for Inorganic Membrane Studies and the Frances B. Manning Professor of Chemical Engineering, and his team (which currently includes two research assistant professors, Erik Engwall and Ivan Mardilovich, and four Ph.D. students), have developed technology that could become the heart of a hydrogen refueling network for cars within a decade or so.
Since 2001, the research has benefited from more than $2 million in funding from Shell International Exploration & Production Inc. and Shell Hydrogen. Shell has invested more than $100 million in hydrogen research since 1999 and wants to be the first company to develop a successful hydrogen refueling system.
Ma’s approach to hydrogen production uses an ultrathin membrane made of palladium. The membrane is integrated with a reactor that employs steam reforming and catalysts to extract hydrogen from natural gas. The palladium membrane allows only the hydrogen to pass through; high-pressure carbon dioxide, the other primary product of the reaction, can be stored for sequestration or used in enhanced oil recovery.
The technology offers several advantages over existing hydrogen production systems. For one, the reactor can operate at significantly lower temperatures than conventional reactors (e.g., 500˚ C versus 700 to 900˚ C), which means it can be made from less-expensive materials. It also combines, in a single device, the processes of generating and separating the hydrogen, which will dramatically cut both operating costs and the size of the reactor, help-ing pave the way for distributed applications.
“Making hydrogen is a well-developed process that involves several steps,” says Ma, “including high-temperature reforming, low- and high-temperature shifts, and preferential oxidation and separation. Our breakthrough was finding a way to lump all of these processes into a single-unit operation.”
“We believe that we have developed one of the best processes available for building palladium membranes on porous metal supports. But we also know there are other competitors out there, so we have to keep making progress to maintain our edge.”
One of the most important milestones during the course of the research was a patented process for building the palladium membranes, which can be as thin as 10 microns. Ma and his team first began working with palladium membranes in the early 1990s with large multiyear research grants from two semi-nonprofit agencies in Taiwan. “During that time, I made a decision that could have turned out good or bad,” Ma says. “Fortunately, it turned out to be very good.”
The diagram illustrates the WPI reactor that will convert methane into pure hydrogen for use in fuel cells. Methane and water, as steam, enter the reaction chamber (A) at one end. From these starting products, steam reforming and catalysts produce hydrogen and carbon dioxide. The central stainless steel tube, which is closed at one end (D), is coated with an ultrathin palladium membrane (C) that lets only hydrogen through; the hydrogen exits at the tube’s open end (B). The photomicrographs show the palladium membrane applied to the stainless-steel support, with an oxide layer in between the palladium and the metal to prevent the membrane from being contaminated by metal components.
The decision was to build the membrane on a porous metal support, rather than the more common ceramic support. Ma knew it would be easier to build a membrane supported by metal into a metal reactor, but he also knew that the components of a stainless-steel substrate could contaminate the palladium at high temperatures, thereby significantly decreasing its effectiveness. His team solved the problem by developing a method of “growing” a protective oxide layer on top of the steel, then forming the palladium membrane on top of that.
This process earned Ma, who is a fellow of the American Institute of Chemical Engineers, and his team a patent in November 2001. It was also around that time that Shell, which had been carefully studying the progress of various academic research teams working on novel hydrogen production techniques, learned about the patented membrane technology and decided to make it the centerpiece of its plans for the hydrogen economy.
“We believe that we have developed one of the best processes available for building palladium membranes on porous metal supports,” says Ma. “But we also know there are other competitors out there, so we have to keep making progress to maintain our edge. With the support we’re receiving from Shell, we hope to keep doing just that.”firstname.lastname@example.org
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Last modified: Apr 28, 2005, 09:14 EDT